The technology of the present disclosure relates to an optical scanning device and an image forming apparatus including the same.
There has been known an opposed scanning type optical scanning device provided with a light source that irradiates a first light beam and a second light beam toward a rotating polygon mirror at one side of the rotating polygon mirror, and irradiates a third light beam and a fourth light beam toward the rotating polygon mirror at the other side thereof. The first to fourth light beams correspond to yellow, magenta, cyan, and black, respectively. The first to fourth light beams are deflected and scanned by the rotating polygon mirror and then are lead to a surface (a surface to be scanned) of an image carrying member corresponding to each color.
In this type of optical scanning device, there is a case in which the rotating polygon mirror is arranged at a plurality of stages in an axis direction in order to facilitate separation of the four light beams deflected and scanned by the rotating polygon mirror. However, in this case, there is a problem that a space for arranging the rotating polygon mirror increases and costs also increase.
In this regard, there has been proposed an optical scanning device capable of configuring the rotating polygon mirror with one stage and separating four light beams from one another. In this optical scanning device, the wavelengths of a first light beam and a second light beam become different from each other and the wavelengths of a third light beam and a fourth light beam also become different from each other. At one side of the rotating polygon mirror, a first optical element is arranged to reflect the first light beam toward a first surface to be scanned and allows the second light beam to pass therethrough, and at a radially outside of the first optical element, a second optical element is arranged to reflect the second light beam, which has passed through the first optical element, toward a second surface to be scanned. At the other side of the rotating polygon mirror, a third optical element is arranged to reflect the third light beam toward a third surface to be scanned and allows the fourth light beam to pass therethrough, and at a radially outside of the third optical element, a fourth optical element is arranged to reflect the fourth light beam, which has passed through the third optical element, toward a fourth surface to be scanned.